Amphibians yield new parasite species


Professor Louis du Preez from North-West University has discovered five new parasite species in the rain forests of French Guiana in South America.

frogs-text2 The worm-like caecilian in which the rare polystome was found.

frogs-text3 A microscopic image of a polystome.

frogs-text4 The 120-kilometre journey upstream on the Approuague River was undertaken in a banana boat. All equipment had to be taken with and because it rained every day, everything had to be covered.
(Images: North-West University)

Prof Louis du Preez
North-West University
+27 18 299 2372

Wilma den Hartigh

A renowned South African researcher has discovered five new parasite species – considered by many scientists to be nigh impossible to find – in the rain forests of French Guiana in South America.

Professor Louis du Preez from North-West University (NWU), who is an expert on flatworm parasites that live in amphibians and fresh water turtles, didn’t know that his research mission to the remote South American forests would yield such a remarkable find.

Du Preez says the parasite species were found in a caecilian, a legless earthworm-like amphibian, in turtles and in a frog.

“We knew beforehand that chances of finding this caecilian were slim, and those of finding the parasite in one even slimmer,” he says.

“Our best scenario was to get one, and we got five.”

Answering questions about amphibians

He says although the discovery is not of veterinary or economic importance, it will help researchers to answer important evolutionary questions about amphibians and their geographical location.

“Now that we have the DNA of the parasite we can find out how its hosts evolved,” he says. “Amphibians were around long before dinosaurs, yet they survived when dinosaurs became extinct.”

Du Preez, who is also an authority on frogs, says it is important to research these amphibians as their survival is critical for a healthy ecosystem.

Frogs are the most threatened vertebrate group in the world because of habitat destruction and the threat of disease and fungi.

“Frogs are important because they eat vast quantities of potentially harmful insects and serve as staple food for some birds and reptiles. Wherever frog numbers are in decline, there is a disruption in the ecosystem.”

An unusual research trip

Du Preez’s search for the parasites started when the National Museum of Scotland contacted him about a parasite they discovered in a caecilian which had been preserved in a bottle of formalin for 120 years.

Scientists were examining the specimen as part of a study on the reproductive organs of caecilians.

But the scientists couldn’t study the DNA as it had been destroyed by the formalin.

The only solution was to find a living sample – and the aim of the research mission was to find the parasites in a caecilian so that the DNA could be extracted.

“We needed to search for a live parasite,” Du Preez says. “It was a huge gamble because we were told that we didn’t stand a chance, but we decided to go and look anyway, and on day two we found it.”

Into the jungle in a banana boat

A team consisting of Du Preez, Oliver Verneau from the French National Centre for Scientific Research (CNRS) and an NWU postdoctoral student, Mathieu Badets, travelled to the virtually inaccessible area of the French Guiana forests in search of the elusive parasite.

Du Preez describes the research mission and discovery as one of his career highlights.

They first stayed at the CNRS base in Cayenne before embarking on a gruelling 120-kilometre trip upstream on the Approuague River in a dugout canoe, also known as a banana boat.

“It took seven hours to travel up the river to reach our destination,” he tells.

The team was based at a remote French scientific research base in the Nouraques Reserve next to the river.

“There are no roads to access it, and the only way is by helicopter, which is very costly, or a banana boat, which is much more cost effective,” Du Preez explains.

They had to take all their equipment and microscopes with them, but the base is well equipped with basic infrastructure and food kept in freezers.

The base lies only four degrees north of the equator and du Preez says the team had to work in hot and rainy tropical conditions, with a constant threat of venomous snakes and jaguars.

“We never slept on the floor. I spent two weeks sleeping in a hammock while at the research base,” he says.

Finding the parasites

Du Preez explains that they were only allowed to catch two kinds of aquatic turtles as part of their research.

The turtles were kept in containers filled with water, after which the water was examined for the parasites. Three aquatic caecilians were also caught in the reserve and in one of the caecilians they found the rare polystome, or flatworm.

“Now, at last, we could extract the DNA from the parasites to see where they fit into the evolutionary development process,” Du Preez says.

He says these discoveries can help to establish how the parasites developed and how they spread across the earth over geological time, as this group of parasites is species-specific.

He adds that amphibians are the first group of vertebrates that moved onto dry land, even before dinosaurs.

“The parasites found in the group of aquatic animals consequently give us a good indication of when this movement occurred in geological time.”

Answering more questions

Du Preez says the discovery of the unique parasites will be keeping scientists very busy in months to come. He is in the process of analysing the new species and describing them, but their research has created even more questions.

He expects to return to the rain forests to do more research next year.

“It was an incredible place to do research and we have been invited by the CNRS to visit the base again.”